The role of surfactant concentration
Surfactant is a substance that can form an interfacial film at an interface, form a colloid in a solvent, and significantly reduce the surface energy of water. Surfactants include ionic surfactants (including cationic surfactants and anionic surfactants), nonionic surfactants, amphoteric surfactants, complex surfactants, and other surfactants.
Surfactants are divided into ionic surfactants (including cationic surfactants and anionic surfactants), nonionic surfactants, amphoteric surfactants, complex surfactants, and other surfactants.
In surfactant solution, after the concentration of surfactant reaches a certain value, the surfactant molecules will form a variety of ordered combinations called micelles. Micellization or micelle formation is a very important basic property of surfactant solutions, and some important interfacial phenomena are related to the formation of micelles. Under certain conditions, the surfactant will also appear anti-micellar state.
Surfactant-protein interactions: Proteins contain non-polar, polar and charged groups, and many amphiphilic molecules can interact with proteins in various ways. Surfactants can form molecularly ordered assemblies with different structures under different conditions, such as micelles, anticlusters, etc., and their respective interactions with proteins are also different. While nonionic surfactants mainly interact with proteins through hydrophobic forces, the interaction between their hydrophobic chains and the hydrophobic groups of proteins can have a certain effect on the structure and function of both surfactants and proteins. Therefore, the type, concentration and system environment of the surfactant determine whether the surfactant stabilizes or destabilizes, aggregates or disperses the protein.
When the concentration of surfactant is very low, there are very few active agent molecules on the surface of water and the surface tension of water does not decrease much. When the concentration of active agent is slightly increased, active agent molecules begin to gather on the surface of water, so that the surface tension of water decreases significantly, and at the same time, the active agent in the water also begins to gather and form a small number of micelles. Continuing to increase the concentration of active agent, many molecules of active agent at the water-oil interface can form a densely arranged monomolecular film, and the micelles below the water surface increase into a spherical shape, and the surface tension of water drops to a lower value. Further increase the concentration of active agent, because the water surface has formed a dense arrangement of single molecule membrane, the state will not be significantly changed, the spherical micelles below the water surface increase, the surface tension of water will not be significantly reduced.
Therefore, the addition of a small amount of surfactant to water can significantly reduce its surface tension, and after reaching a certain critical value, the change in surface tension is very small. In practice, the amount of surfactant added must be tested, optimized and strictly controlled within a better range.
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